In a wireless sensor network, if neighboring nodes transmit data packets of their own at the same time, collision will occur. As shown in FIG. 1, a node A and a node C occupy identical slots to transmit data packets of their own. And as for a neighboring node B, as it receives data packets at this slot, obvious collision is produced.
Currently, in order to overcome such collision, a slot assignment method is used, so as to ensure that neighboring nodes transmit data packets of their own at different slots. As shown in FIG. 2, a node A transmits its data packets at a slot n, a node C transmits its data packets at a slot m, and as for a neighboring node B, it receives data packets transmitted by the node A and the node C at different slots. So transmission collision may be avoided, and fewer packets will be dropper, a higher delivery ratio will be achieved.
However, in the implementation of the present invention, the inventors found that for slot allocation of a node, a slot length and a slot sequence number (a slot index) need to be determined. An improper slot index will possibly result in relatively long time delay. As shown in FIGS. 3a and 3b, nodes A and B have a data packet respectively, and a slot allocation scheme shown in FIG. 3a and a slot allocation scheme shown in FIG. 3b have identical slot lengths, that is, two slots are allocated to the node A and one slot is allocated to the node B. In the slot allocation scheme shown in FIG. 3a, SINK (sink node) may collect all the data packets by using three slots, but in the slot allocation scheme shown in FIG. 3b, it is impossible to complete the collection within three slots, and more than three slots are needed.
It should be noted that the above description of the background art is merely provided for clear and complete explanation of the present invention and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background art of the present invention.